Production of synthetic tanning agents



' depending,

Patented Mar. 29, 1932 I UNITED" STATES PATENT OFFICE CORPORATION 01 GER-HAN! I BGHUE'ITE, OF ILNNHEII, GERKANYyASSIGNOR TO I. G. F-

DUB'I'BIE' AKTIENGESELLSCHAI'I', OF FRLNKFOBT-ON-THE-MAIN, GERMANY, A

PBODUOIION OF SYNTHETIC TANNING AGENTS Io Drawing. Application filed August 11, 1928, Serial No. 299,098, and in Germany August 23, 1827.

The present invention relates to the production of synthetic tanning agents.

.1 have found that a new group of valuable synthetic tanning agents can be obtained by condensing a methylol compound of a monohydric phenol with resorcinol at a temperature below 50 C. in the presence of water and, preferably, of small amounts of a condensing agent either of acid or alkaline o nature. The amount of condensing agent to be employed varies with the'temperature employed, smaller amounts being employed on working at ahigher temperature whereas on working at alower temperature the amount of condensing agent can be increased without producing water-insoluble products. The products obtained according to this invention have very good tanning propertles and differ from most of the artificial tanning materials hitherto known, by the absence of the -sulfo group.

The methylol compounds of a monohydr1c phenol employed as initial materials may be prepared in any convenient manner, for ex- 2; am le, according to the particulars given in the S. A. Patents Nos. 526,786 and 563,975 by condensing a monohydric phenol of the benzene series with formaldehyde in the presence of neutral or alkaline condensing :0 agents; thus, for instance, an aqueous solutlon containing up to 5 or 6 molecular proportions of formaldehyde may be allowed to act upon 1 molecular proportion of phenol. According to the process of the present invention the methylol compounds. of a monohydric phenol obtained by a process of this kind need not be isolated from the aqueous solution as the solution may be brought directly into reaction with resorcinol. The

amount of resorcinol to be employed per each molecular proportion of the methylol compound of a monohydric phenol is preferably.

' chosen so as to be sufiicient to provide 1 molecular proportion of resorcinol for each methylol group present in the phenol alcohol, but it may also be smaller.

This method of operation furnishes a variety of products which, according to the nature and amount of the initial materials, for example, on the amount of preparation of the methylol compound of a monohydric phenol on the other hand, differ among themselves by the degree of their solubility in water. The tanning agents prepared with larger amounts of resorcinol and with methylol compounds of a monohydric phenol which are richer in methylol groups, are readily soluble in water, and produce a light coloured leather of good body and in a hlgh yield, which is practically equivalent to that obtained with the aid of weight-giving vegetable tanning extracts. The tanning agents prepared from smaller quantities of resorcinol and from methylol compounds of a monohydric phenol with fewer methylol groups are less soluble in water and are comparable with the sparingly soluble quebracho extract. The last-named condensation productsin particularare preferably employed for tanning'in the presence of the well known dispersive-sulfonic acids, such as aromatic sulfonic acids of high molecular weight or condensation products of sulfonic acidswith formaldehyde and the like, which may also possess tanning properties,- in which case also a firm, compact and weighty leather of excellent character is produced. The new tannlng agents may also be used, with advantage, in admixture with other tanning or non-tanning substances usually employed in tanning processes, such as vegetable tanning Example 1 A solution of 94 parts by weight of phenolin 400 parts by volume of a 10 per cent solution of caustic soda, is treated with 220 parts by weight of a 30 per cent aqueous solution of formaldehyde, and diluted with water to make 1100 parts by volume. After standing for several days, during which time theform- 190 aldehyde disappears, the solution is exactly neutralized with dilute sulfuric acid, whereupon a solution of 220 parts by weight of resorcinol in 280 parts by weight of water and 10 parts by volume of concentrated hydrochloric acid is added. After again standing for several days, thewateris driven off to a large extent by moderate heating in vacuo, the reaction product separating out 1n the form of a pale reddish-yellow, wax-like mass, which is only partially soluble in water. "400 parts by weight of this substance are next triturated with 800 parts by wei ht of a 50 per cent aqueous solution of the su fonic acid, obtained in accordance with the Examle 1 of U. S. Patent No. 1,557,844 and leached in the manner described. The resulting viscous paste can be diluted with water in any proportions and, when em loyed for tanning, produces a pale 'yellowrown leather of good body which is satisfactorily compact and weight The analysis of the tannlng agents by the agitation method shows an increase of 110 per cent of tanning agent calculated on the content of the sulfonic acid in the tanning matter.

Ewample 2 A solution of 94 parts by weight of phenol in 400 parts by volume of a 10 er cent caustic soda solution, is treated with 330 parts by weight of a 30 per cent aqueous solution of formaldehyde, and diluted to 1200 parts by volume with water, and after standing for several days, is neutralized with dilute sulfuric acid. It is then treated with an addition of 330 parts by weight of resorcinol, dissolved in 400 parts by weight of water and 10 parts by volume of concentrated hydrochloric acid; after standing again for several days, most of the water is eliminated in vacuo and'a product similar in character to that described in Example 1 is obtained.

Triturating 400 parts by weight of this substance with 1200 parts by weight of the not wholly neutralized sulfonic acid prepared in accordance with Example 1 of U. S. Patent No. 1,237,405 results in the formation of a syrupy mass, which is readily soluble in water and, when employed for tannin produces a light reddish leather of goo body which is firm and compact andweiglhty. The analysis of the tanning agent by t e method of agitating with hide powder shows an increase of 54 per cent of tanning agent calculated on the content of the sulfonic acid in the tanning matter.

In the place of h drochloric acid, sulfuric or acetic acid or acid sodium sulfate or sodium hydroxid can be employed as condensing agent. 7

- Example 3 158 parts by weight of finely powdered barium hydroxid are introduced into a soluwater 6.2 per cent. a pale reddish leather of good body is ob-.

tion of 94 parts by weight of phenol in 600 parts b weight of a 30 per cent aqueous solution 0 formaldehyde. After standing for several days, the barium h droxide is precipitated by a current of car 11 dioxid, the deposited barium carbonate is filtered ofl, and the filtrate is treated with a solution of 550 parts by weight of resorcinol in 600 parts of water and 10 parts by volume of concentrated hydrochloric acid. After again standing for several days, the solution is concentrated in vacuo to the consistency of a tanning extract, a pale reddish syrupy mass being obtained which can be readily diluted with water. The tanning analysis, by the filtration method, of a product with a density of about 32 B., shows tanning matter 50.4 per cent; nontanning matter 15.6 er cent; insolubles in en used for tanning,

tained in a high yield.

What I claim is:

1. The process of producing water soluble synthetic tanning agents which comprises condensing a methylol compound of a monohydric henol with resorcinol at a temperature be ow 50 C. the presence of water and of a small amount of a condensing agent.

2. The process of producing water soluble synthetic tanning agents which com rises condensing an aqueous solution of a met ylol compound of a monohydric phenol with resorcinol at a temperature below 50 C. and in the presence of water and of a small amount of a condensing agent.

3. The process of producing water soluble synthetic tanning agents which com rises condensing at a temperature below 50 and in the presence of water and of a small amount of a condensing agent a methylol compound of a monohydric phenol with an amount of up to one molecular proportion of resorcinol per each methylol group contained in the aforesaid methylol compound.

4. The process of producing water soluble snythetic tanning agents which com rises condensing at a temperature below 50 and in the presence of water and of a small amount of an acid -condensing agent a methylol compound of a monohydric phenol with an amount of up to one molecular proportion of resorcinol per each methylol group present in the aforesaid methylol compound.

5. The process of producing water soluble synthetic tanning agents which comprises condensing at a temperature below 50 C. and in the presence of water and of a small amount of a condensing agent a methylol compound of phenol with an amount of up to one molecular proportion of resorcinol per each methylol group present in the aforesaid methylol compound.

6. Asnew articles of manufacture synthetic tanning agents comprising a. water soluble Condensation roduct of a methylol compound of a monohy ric phenol with resorcinol.

I 7 As new articles of-manu facture synthetic tanning agents comprising a water soluble condensation product of a methylol compound of a monohydric' phenol with an amount of up to one molecular proportion of resorcinol per each methylol grou present in the aforesaid methylol compound 8. As new articles of manufacture synthetic tanning agents comprising a water soluble condensation product of a methylol compound of a monohydric phenol with resorcinol and an organic sulfonic acid possessing dis- 15 persive properties.

' 9. As new articles of manufacture synthetic tanning agents comprising a water soluble condensation product of a methylol compound of a monohydric phenol with resorcinol 0 and anorganic sulfomc acid possessing dispersive and tanning properties.

In testimony whereof I have hereunto set my hand. a 25 HERMANN SGHUETTE. 

